Method and apparatus for dispersing divided solid material in gas



July 11, 1933. M, A, ss N 1,917,266

METHOD AND APPARATUS FOR DISPERSING DIVIDED SOLID MATERIAL IN GAS FiledJuly '7, 1951 4 Shets-Sheet l INVENIOR. MflceZA.Zzss/mz/g 5 Mob/Z I lATTO NEYS. r-:

' .Fuly 11, 1933.

M. AQLISSMAN 1,917,266

METHOD AND APPARATUS FOR DISPERSING DIVIDED SOLID MATERIAL IN GAS FiledJuly 7, 1951 4 Sheets-Sheet 2 q B .24 2a INVENTOR. I MaficeZ 1T .Lwsmam,

Juliy M, 1933. Y M. A. LISSMAN METHOD AND APPARATUS FOR DISPERSINGDIVIDED SOLID MATERIAL IN GAS Filed July 7, 1931 4 Sheets-Sheet 3INVENTOR jfiwceZ/I. l7 wsmalg BY%% M i/ M ATTOR EYS.

M. A. LISSMAN July 11 1933.

METHOD AND APPARATUS FOR DISPERSING DIVIDED SOLID MATERIAL IN GAS FiledJuly '7, 1951 4 Sheets-Sheet 4 Patented July 11-, 1933 UNITED STATESPATENT OFFICE MANCEL A. LISSHAN, OF ALHAMBRA, CALIFORNIA, ASSIGNOB 'IO,INTERNATIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA, ACORPORATION OF CALIFORNIA METHOD AND APPARATUS FOR DISPERSING DIVIDEDSOLID MATERIAL IN GAS Application filed July 7,

the invention is to provide a novel and advantageous method andapparatus for effecting such dispersion, and articularly for effectingas complete as possi 1e a dispersion or separation of the individualparticles of solid material from one another. The invention isparticularly useful in the dispersion of material containing aconsiderable proportion of fines or flour, the particles of which tendto adhere to one another or to larger particles.

In elutriation and classification of divided solid material involvingsuspension of such materials in a stream of air or other gas, one of themost important requirements for maximum efiiciency and sharpness ofseparation of particles of different sizes is the obtaining of themaximum dispersion or separation of the individual particles, and thisrequirement has heretofore been met only in a very crude manner. Inelutriation, it is customary to have an air stream play upon the sampleand so gradually disperse it. However, when it is desired to separatethe finer fractions, it is found that the air stream has a packingeffect upon portions-of the sample, and the energy in the air stream isinsufiicient to wash off or dislodge the adhering fines from the coarserparticles, thus preventing complete dispersion and resulting in failureto obtain a sufficiently sharp and complete separation of sizes.

In classification, it is customary to feed the material into an airstream having a sufficiently high velocity to substantially preventsettling of such material therein, so that the material is carried alongby the air stream to the classifying means. In order to obtain completedispersion in this manner, the velocity of the air stream and'the volumeof air required become prohibitively large, and

the velocities and volumes of air ordinarily employed result only inveryimperfect dispersion. Even then a classifying means is required tohandle a large amount of excess air and must therefore be of large sizeand great expense, while the excessive power re- 1931. Serial No.549,152.

quirements involved in furnishing the desired volume and velocity of airconstitute a further source of considerable expense.

According to the present inventlon, the dispersion of divided solidmaterial in gas is obtained by making use of the characteristics of arapid vortical motion of a circulating. body of air or gas confinedwithin a container .of circular cross-section and preferably ofcylindrical or frusto-conical form. The divided solid materials which itis desired to disperse are introduced into the vortex and, due to therapidity of the vortical motion, are

a continuously subjected to high radial accelerations and are caused torepeatedly cross the stream lines of the vortical motion, and are thussubjected to an extremely vigorous shear-' ing action at the surface ofthe particles which effectively breaks up adherin clusters of particlesand washes the fines o the surfaces of the coarser particles. The solidmaterial thus dispersed in the air stream is continually removed fromthe container in suspension in only a relatively small proportion of thegas stream, such removal being preferably effected at or adjacent theperiphery of the vortex, where the concentration of dispersed solidmaterial is the greatest. A small amount of air is continuously admitedto the container at a point of relatively low pressure in the vortex, tocompensate for the air discharged with the dispersed material. Only aVery small amount of air is thus re uired for actually transporting thedisperse material from the dispersion apparatus, requiring a minimumamount of power and a classification or elutriation apparatus ofrelativel small size. Furthermore, the power required for maintainingthe vortical motion within the dispersion apparatus is relatively smallbecause it is only necessary to supply suflicient energy to overcome thefriction of the whirling gas against the walls of the container, due tothe fact that the gas is repeatedly circulated in the vortex and servesfor dispersion present invention are intended-particularly for use inelutriation and classification apparatus, 'they may be used, in general,where ever it is .desired to disperse dlvided solid material in a gasstream, for example for obtaining complete dispersion of a sample ofpowdered material in air or gas for use in makin tests, to determine theeficiency of collection obtainable with that particular powderedmaterial in any certain type of collecting a paratus, such as a cycloneseparator bag lter, or the like.

. nother field of utility of this invention is in the application ofinsecticides or similar agents in owdered form, b dusting the same intothe air from suitable ispersing apparatus carried by aeroplane overareas of growing trees or plants and allowing the same to fall uniformlyupon such trees or plants. In such cases it is important, for mosteficient results to secure as thorough as possible a dispersiori of thepowdered material into the air, for which purpose the method andapparatus of the present invention are particularly well adapted.

The accompanying drawings illustrate certain forms of apparatusaccording to the present invention, and referring thereto:

Fig. 1 is a partly sectional side elevation of one form of suchapparatus.

Fig. 2 is a plan view thereof.

Fig. 3 is a horizontal section on line 33 in Fig. 1.

Fig. 4: is an enlarged sectional view on line 44 in Fig. 1.

Fig. 5 is a section on line 5-5 in Fig. 4:.

Fig. 6 is a vertical section of another form of such apparatus.

Fig. 7 is a horizontal section on line 77 in Fig. 6.

Fig. 8 is a vertical section showing a modification in the shape of thedispersion cham ber of an apparatus of the general type shown in Figs. 6and 7,

The form of apparatus shown in Figs. 1 to 5 inclusive, comprises acylindrical housing or container 1 comprising cylindrical side wall 2and top and bottom walls 3 and 4: respectively, the interior of saidhousing constituting a cylindrical dispersion chamher A. A centrifugalfan impeller 5 is rotatably mounted in the lower portion of saidchamber, said impeller being mounted on shaft 6 extending through anopening 7 in the bottom wall 4 and driven by electric motor 8. The axisof rotation of the fan impeller preferably coincides substantially withthe axis of the chamber A. The opening 7 is of somewhat larger diameterthan shaft 6, so that a limited quantity of air may be drawn into thechamber at this point, which is obviously a point of relatively lowpressure in the vortex. The side wall 2 is shown as having its lower endportion 2a inclined inwardly and downwardly around the fan impeller, asshown.

The divided solid material may be delivposed between said fixed plates.

aei'aaes ered into the dispersion chamber through a 'feed hopper 11disposed above said chamber and within a frusto-conical upper housing 12extending upwardly from the top wall 3 and secured to the upper edge ofsaid hopper. Said hopper is formed with a cylindrical delivery spout 13through which the solid material passes to a feed opening 14 in the topplate 3. The rate of flow of solid material to said feed opening ma becontrolled and maintained uniform 2 y a suitable valve mechanismcomprising, for example, two spaced plates 16 and 17 rigidly securedwithin the botom portion of the cylindrical spout 18 and a rotary plate18 dis- The lower fixed plate 17 is shown as provided with an opening17' disposed directly over the opening 14 while the upper fixed plate 16is such as provided with an opening 16 diametrically opposite theopening 17,each of said openings extending through an arc of somewhatless than 90, as shown in Fig. 5. The rotary plate 18 is provided withtwo diametricall opposed openings 18' each extending through an arc ofapproximately 90, so that upon rotation of said rotary plate each ofsaid openings 18 is brought first beneath the opening 16' so as toreceive a measured quantity of material from the hopper and issubsequently brought to position over the opening 17 so as to dischargesuch quantity of material through said last-named opening and throughthe opening 14: into the dispersion chamber. The rotary plate 18 may besecured to the lower end of a shaft 19 which extends through a centralopening in plate 16 and is driven by electric motor 21 which is shown asoperatively connected thereto through variable speed pulleys 22 and 23,belt 24 and reducing gear means 25. The upper end of hopper 11 may beopen and the material may be delivered thereto through chute 27.

An outlet pipe 31 communicates substantially tangentially with thechamber A at the periphery thereof and adjacent the top of said chamber,through an opening 32 in the side wall 2. Said outlet opening and pipeare preferably of relatively small size as compared to the capacity offan 5, so that only a relatively small portion of the totalrecirculating gas is directed through said outlet opening and pipe.

In the operation of this form of apparatus the fan impeller 5 is rotatedat high velocity by means of electric motor 8 and causes the air withinthe chamber A to be set in rapid vortical motion, in which the air isforced outwardly between the fan blades at the lower portion of thechamber, thence upwardly in a rapidly whirling outer vortex such asindicated at V then inwardly toward the axis of the chamber at the upperend thereof and thence downwardly in an inner vortex indicated at V tothe center The divided solid material to be'dispersed' is-delivered intothe vortical gas movementwithin the chamber by operation of the feedingmeans as above described, and is picked up by the whirling gas withinthe inner vortex and subjected thereby to centrifugal action. Thecoarser particles are, in general, driven by this centrifugal force intothe upwardly moving outer vortex before reachin the position of the fan,while some of the ner particles may be carried downwardly with the air,through the fan impeller, and thence upwardly. The rapid motion of theair relative to the particles of solid material, in both the inner andouter vortices serves to shear or tear the particles from one anotherand to break up adhering clusters thereof.

The shearing action is especially intense and effective in the regionadjacent the periphery of the dispersion chamber. The particles in thisregion are thrown by centrifugal force against the side wall of saidchamber, and some of the particles, particularly the coarse particles,are caused to rebound therefrom out into the gas stream again, and theaction is then repeated. Other particles re main close to the side wallbut are repeatedly rolled over and over and, due to local eddy currents,are from time to time picked up by the gas and carried forward, to beagain thrown out against the side wall. All of the particles are thuscaused to repeatedly cross the stream lines of the rapid air movementand are thus subjected to a vigorous washing action.

As the air reaches the upper end of the vortical chamber a portionthereof, together with the dispersed solid material contained therein atrelatively high concentration, is discharged through the tangentialoutlet means 31, while the remainder of the air and, in generahsome ofthe finer particles of solid material, are recirculated in the chamberand repeat the above cycle of operations.

The form of apparatus shown in Figs. 6 and 7 comprises a verticallydisposed cylindrical housing 1 inclosing a dispersion chamber A, saidhousing including as before a cylindrical side wall 2' and top andbottom walls 3' and 4'. The centrifugal fan indicated at 5 is in thiscase located adjacent the upper end of chamber A and is mounted forrotation about the axis of said chamber. Said fan is secured to shaft 6driven by electric motor 8 mounted on a suitable supporting structure asshown. 7

In this form of the invention the bottom wall 4' is shown as comprisingan inwardly extending substantially horizontal annular portion 4a and aninwardly and upwardly inclined frusto-conical central portion 46'provided with a central air inlet opening 7 The outlet means is shown ascomprising an outlet pipe 31 communicating substantially tangentiallywith the lower end of chamber .A at the periphery thereof, throughopening 32. The admission of air through opening 7 may be controlled bymeans of .a tapered valve member 36 which is vertically operable towardand away from said opening by any suitable operating means such as rod37 and lever 38. Suitable positioning means 39 may also be providedcooperating with said lever to hold said valve in any position ofadjustment. Lever 38 is pivotally mounted at 41 and is provided with ahandle 42 for manual operation thereof, the other end of said leverbeing pivotally connected to rod37 as at 43. Fixed guide means 44 engagerod 37 so as to keep the valve member 36 substantially centered withrespect to opening 7 I The centrifugal fan 5' is shown in this case asprovided with a horizontal disc or plate 46 disposed above the fanblades, and the divided material to be dispersed is delivered into thevortical gas movement by feeding the same onto said plate through anopening 47 in the top wall 3. The means for supplying material to saidopening is shown as comprising a feed hopper 48 and screw conveyor 49,said screw conveyor being preferably driven by the same driving means asthe centrifugal fan 5. For this purpose the shaft 51 of said screwconveyor is shown as operatively connected to the electric motor 8' bymeans of gear 52 on said shaft 51, meshing with gear 53 on a shaft 54which may be operatively connected or disconnected to shaft 54 bysuitable clutch means 56, said shaft 54 being connected through bevelgears 57, shaft 58, pulley 59 and belt 61 to pulley 62 on the motorshaft 6. By this means the speed of operation of the screw conveyor 49,when clutch means 56 is in engagement, is always proportional to thespeed of opera tion of the centrifugal fan 5, so that the rate of feedof divided material into the dispersion chamber is substantiallyproportional to the velocity of vertical gas movement therein, while thesupply of divided material may be cut off at any time by disengagementof'clutch means 56, while vthe centrifugal fan and driving motor areleft in operation. This form of apparatus is, therefore, particularlyadapted to cases in which it is desired to intermittently interrupt andresume the delivery of dispersed solid materials from the apparatus, asfor example in the above mentioned application of insecticidal dusts orpowders or the like.

The operation of this form of apparatus the downwardly moving outervortex V differs from that of the form first described, chiefly in therelative position of introduction of the finely divided solid materialwith respect to the vortical gas movement. In this case the gas isforced outwardly by the fan at the upper end of the chamber and passesdownwardly in a rapidly whirling outer vortex V thence inwardly towardthe central portion of the chamber and upwardly in an inner vortex V tothe central portion of the fan. The divided solid material delivered byconveyor 49 falls through opening 47 upon the rapidly whirlindistributing plate or disc l6, which pic s up the material and throws itoutwardly by centrifugal force over the edge of said plate or disc andagainst the side wall of the chamber, where the material is picked up bythe gas discharged from the ends of the fan blades and is carried alongwith the gas in The whirling gas acts to separate and disperse the solidparticles in substantially the same manner as above described so that bythe time the solidmaterial reaches the lower end of the chamber it is insubstantially completely dispersed condition. A small portion of the gasfrom the outer vortex is continually diverted through the outlet means31 and carries with it in suspension this dispersed solid material. Acorresponding amount of gas is continually drawn in through the opening7 and passes upwardly along with the recirculating gas in the innervortex.

As stated above, the delivery of dispersed solid material from theapparatus may be cut off at any time without interrupting the operationofthe. fan, by simply disengaging the clutch 56 so as to stop operationof conveyor 4191 Upon reengaging said clutch, the feed of divided solidmaterial into the apparatus is resumed and the delivery of such materialfrom the apparatus in dispersed condition starts almost immediately, aparticular advantage of the above arrangement being that operation maybe thus suspended and again resumed without requiring any delay forbringing the fan up to speed and establishing the vortical gas movement.

The form of apparatus shown in Fig. 8 is substantially the same as thatshown in Figs. 6 and 7 with the exception that the side wall 2" of thedispersion chamber housing is frusto-conical instead of cylindrical inshape and tapers inwardly from the upper end at which the centrifugalfan 5 is located toward the lower end at which the gas outlet 31 islocated. Except for this difference the parts of the apparatus are ofthe same construction and relative arrangement as above described inconnection with Figs. 6 and 7, and are similarly numbered in thedrawings. The operation of this form of apparatus is mamas alsosubstantially the same as in Figs. 7 and 8 with the exception that theouter descending vortex decreases in diameter as it passes downwardly,and a somewhat larger proportion of the gas may thus be caused to passfrom the outer vortex into the ascending inner vortex before reachingthe lower end of the chamber than is the case whena cylindrical chamberis used.

It will be seen that in the operation of each of the forms of apparatusabove described, a vortical movement of gas is continually maintained inthe inclosed dispersion chamber, and the major portion of the gas isrepeatedly recirculated in this vortical movement, a certain proportionof the as however being continually withdrawn rom the vertical movementat one point in the path of circulation of the gases and a correspondingportion of gas being continually introduced at another point in saidpath, and the finely divided solid material to be dispersed is deliveredinto the vortical gas movement at a point somewhat removed from thepoint of gas withdrawal and suificiently in advance thereof in the pathof circulation of the gas to permit substantially complete dispersion ofsuch material in the gas by means of the above described dispersingaction before reaching the gas outlet, the material so dispersed beingcarried off in suspension in the gas withdrawn through said outlet.

More specifically it will be seen that the gas is repeatedlyrecirculated in inner and outer vortices moving in reverse directionslongitudinally of the axis of such movement, such circulation beingeifected by applying a rotative force to the gas at one end of thedispersion chamber so as to maintain the necessary whirling motion andthe necessary difference in pressure between the outer and innervortices at this end of the chamber. While the outer vortex is shown inthe drawings, for the purpose of illustration, as proceeding from theend at which such rotative force is a plied to the gas to the other endof the chamber, it will be understood. that in general, as the velocityof whirling movement decreases in moving toward the other end of thechamber a portion of the gas will continually be forced or drawninwardly from the outer vortex .into the inner vortex and thus have itslongitudinal component ofmotion reversed before reaching the further endof the chamber, but the centrifugal force acting on the particles ofsolid material will-be sufficient to substantially prevent suchmaterial, with the possible exception of the more finely dividedparticles thereof from being thus drawn inwardly along with this portionof the gas, so that substantially all the solid material is carriedalong in the outer vortex to the end of the chamber opposite thecentrifugal fan,

5 is delivered into the vortical gas movement at the end opposite thecentrifugal fan and first enters the inner vortex moving longitudinallytoward said fan and reaches the outer vortex either by being thrown intothe same by centrifugal force or by being carried along with the gasthrough the fan and into said outer vortex. On the other hand, in theforms of apparatus shown in Figs. 6 to 8 inclusive, the material to bedispersed is delivered into the outer vortex at the end adjacent thecentrifugal fan and is carried along in this outer vortex until itreaches the gas outlet at the opposite end thereof, where the majorportion of such material is removed and only the extremely fineparticles may be recirculated with the gas.

I claim:

1. The method of dispersing finely divided solid material in gas whichcomprises maintaining a vortional gas movement within an inclosedchamber, repeatedly recirculating the major portion of the gas in suchvortical movement in such manner that the gas moves repeatedly from oneend of the chamber toward the other end thereof and back again,delivering finely divided solid mateterial into the vortical gasmovement at one point in the path of circulation thereof, removing aportion of the gas containing dispersed solid material in suspensionfrom the vortical movement at another point in said path, andintroducing a corresponding portion of gas to said vortical movement ata point removed from said last named point.

2. The method of dispersing finely divided solid material in gas whichcomprises maintaining a vortical movement of gas within an inclosedchamber while continually recirculating the major portion of such gas ininner and outer vortices moving in opposite directions longitudinally ofthe axis of vortical movement, delivering divided solid material to bedispersed into said vortical movement at one point in the path ofcirculation thereof, removing the portion of a gas containing dispersedsolid material in suspension from the outer vortex at a point somewhatremoved from said first-named point, and introducing additional gas intosaid vortical movement at a point removed from said point of removal ofgas and solids.

3. The method as set forth in claim 2, in which the-solid material to bedispersed is delivered into the outer vortex of the gas adjacent the endof the chamber from which said outer vortex proceeds, and the gas anddispersed solids are removed from the outer vortex adjacent theopposite, end of the chamber. q

4. An apparatus for dispersing finely divided solid material in gascomprising a housing having a circular cross-section whose interiorconstitutes a dispersion chamber, a centrifugal fan mounted within saidchamber and adjacent one end only thereof and rotatable about the axisof said chamber, gas outlet means communicating with said chamberadjacent the periphery thereof at the end opposite said centrifugal fan,means for delivering divided solid material to said chamber at aposition somewhat removed from said gas outlet means, and gas inletmeans communicating with said chamber adjacent the axis thereof.

5. An apparatus for dispersing finely divided solidmaterial in gascomprising a cylindrical housing whose interior constitutes a dispersionchamber, a centrifugal fan mounted within said chamber and rotatableabout the axis of said chamber, gas outlet means communicating with saidchamber at one end thereof and adjacent the periphery thereof, saidcentrifugal fan being located at a part of said chamber remote from theend at which the gas outlet means is located, means for deliveringdividedsolid material to be dispersed into said chamber at a positionsomewhat removed from said gas outlet means, and gas inlet meanscommunicating with said chamber at a position somewhat removed from saidgas outlet means, said gas outlet and gas inlet means being sorestricted in size as to provide outflow and inflow therethrough of onlya relatively small proportion of the gas circulated by said 6. Anapparatus as set forth in claim 5, said gas inlet means communicatingwith said chamber adjacent the axis thereof.

7. An apparatus as set forth in claim 5, said gas outlet meanscommunicating with said chamber adjacent the end opposite saidcentrifugal fan.

8. An apparatus as set forth in claim 5, said gas outlet meanscommunicating with said chamber adjacent the end opposite said fan andthe means for delivering divided solid material being so disposed as todeliver such material into said chamber adjacentthe position of saidfan.

9. An apparatus for dispersing finely divided solid material in gascomprising a housing of circular cross-section'having its axissubstantially vertical, the interior of said i housing constituting adispersion chamber, a

centrifugal fan mounted within said chamber adjacent the upper end onlythereof and rotatable about the axis of said chamber, gas outlet meanscommunicating peripherally with said chamber adjacent the lower endthereof, gas inlet means communicating substantially axially with saidchamber adjacent the lower end thereof, and means for deliver- Ell emmespect to the axis of rotation of said fan, and mleans for deliveringsuch material onto said p ate.

In testimony whereof I have hereunto subscribed my name this 29th day ofJune, 1931. m

MARCEL A. LISSMAN.

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